Filament failure device



1366- 1952 L. L. HELTERLINE, JR, ETAL FILAMENT FAILURE DEVICE 2 SHEETSSHEET 1 Filed Feb. 7, 1948 INVENTOSS LED L.HEL TERLIHE A. MAR CELL US BEE T, JR AND AJJ DLPH E1 UHBLA SKY ATTORNEY D 1952 L. HELTERLINE, JR, ETAL 2,621,322

FILAMENT FAILURE DEVICE f WW n IHVE'NTORS LED L.HE1,TERLINE, 1J9. ARCELLUS BEST, JR AND ADDLPH BUNBLASKY' I ATTORNEY Patented Dec. 9, 1952 UNITED STATES i ATENT OFFICE FILAMENT FAILURE DEVICE of Connecticut Application February 7, 1948, Serial No. 6,865

Claims.

This invention relates to new and useful improvements in electronic tubes and to a voltage regulator employing such tube and has particular relation to a filament failure device for electronic tubes.

An object of the invention is to provide a voltage regulator including an electronic tube having incorporated therein a filament failure device designed to an over-voltage condition which exists in the output of such an instrument or regulator on failure of the tungsten filament diode.

Another object is to provide a voltage regulator comprising a diode tube including a filament failure device of such construction and arrangement that on failure of the filament, the diode becomes a short circuit rather than an open circuit as far as the bridge or balancing circuit of the voltage regulator is concerned. In such as instrument or device, i. e., voltage regulator, the results are an opposite action and the output voltage lowers rather than rises, thus preventing any damage to equipment which may be employed in the output of the instrument or voltage regulator.

A further object is to provide an electronic tube having incorporated therein a filament failure feature of commercial value inasmuch as the cost of incorporating the feature in the tube is not excessive.

A more specific object is to provide a simple and inexpensive means to prevent an over-voltage condition ranging 30%-40% above normal which exists in the D. 0. output of such voltage regulators when the filament of the diode electron tube burns out completely thereby breaking or opening the filament circuit which causes said over-voltage. The means provide upon burnout of said filament to free a spring biased filament electrode connected directly to positive polarity of the D. C. output leads to close or short circuit said connection directly to the plate of the diode tube thereby effecting and increasing the positive grid potential to increase electronic emission in a power tube increasing the plate current and the impedance of a reactor reducing the input and subsequently the output voltage thus eliminating the need of an expansive over-voltage circuit breaker in said output to protect and prevent burnout of instruments connected therein.

Other objects and advantages of the invention will become apparent from a consideration of the following detailed description taken in connection with the accompanying drawings wherein a satisfactory embodiment of the invention is shown. However, it is to be understood that the invention is not limited to the details disclosed but includes all such variations and modifications as fall within the spirit of the invention and the scope of the appended claims.

In the drawings:

Fig. 1 is a side elevational view showing a diode tube constructed in accordance with the invention;

Fig. 2 is an enlarged top plan view of the base and elements of said tube, the envelope being omitted and the parts being in normal condition;

Fig. 3 is a side elevational view of the tube parts shown in Fig. 2, the view being as seen from the lower side of Fig. 2;

Fig. 4 is a side elevational view of the device of Fig. 3, the view being as seen from the right of Fig. 3;

Fig. 5 is a view similar to Fig. 2 but showing the relative positions of the parts following filament failure or breakage;

Fig. 6 is an elevational view taken as looking toward the lower side of Fig. 5;

Fig. '7 is a schematic View showing the connections of the tube parts; and

Fig. 8 is a schematic wiring diagram showing the tube of the invention as employed in the circuit of an electronic voltage regulator.

The present invention relates particularly to the above mentioned electronic tube and its use in a voltage regulator such as that disclosed in application Serial Number 662,751, filed April 17, 1946, now Patent 2,455,143, issued November 30, 1948, or disclosed in application Serial Number 740,953, filed April 11, 1947, both by Edward M. Sorensen. The electron tube described herein is claimed per se in our divisional application Serial Number 84,806 filed April 1, 1949. In Fig. 8 of the present application there is shown an improved voltage regulator resulting from the substitution of the present tube for that disclosed at IS in Fig. 3 of the above mentioned Sorensen application, Serial Number 740,953. The invention also contemplates other uses of said tube and specifically contemplates substitution of the present tube having incorporated therein the filament failure feature for the tube l3 of the voltage regulator disclosed in the above identified Sorensen patent.

Referring in detail to the drawings and at first more particularly to Figs. 1-7, there is shown the arrangement of the elements in our improved diode tube Hl. Said tube comprises an evacuated insulating envelope ll attached to an insulating base l2 provided with pron s or terminals I 3 for engaging suitable electrical contacts in a standard tube socket. The insulating envelope ll includes a bottom wall portion is separated from the base I2. This bottom wall portion securely mounts terminal leads Hi, l6, l1 and I8 passing therethrough and each in electrical contact with a separate prong l3.

Terminal lead I has a right angle bend providing an arm l9 mounting a cylindrical plate electrode 26 welded or. otherwise secured thereto. It will be noted that the arm 19 is in tangential contact with plate 26 and said contact is intermediate the ends of said plate. Terminal lead 16 mounts a right angle extension piece 2|. the horizontal arm of which is rigidly secured to the lead it while the other arm of piece 2| inclines laterally and upwardly of said lead. It will be readily seen that a filament 22 is passed longitudinally and co-axiallv through the cylindrical plate 251 and said filament is welded or otherwise secured at one'of its ends to the laterally and upwardly inclined arm of the rigid extension piece 2| as at 23.

Terminal lead I! mounts an extension piece 24 at right angles thereto, one end of said extension piece being rigidly welded or otherwise secured to said lead near one end thereof as at 25. The end of a resilient cantilever spring wire 26 having a slight bond 27 intermediate its end portions is welded or otherwise secured at one end, as at 28, to the rigid arm or extension 25.. The spring wire 26 is physically or mechanically forced over or urged into a straightened position against the s ring biasing action characteristic of said bend 2! and the force used is of a magnitude so as not to over stress the bend 27 of the spring in any such manner as to prevent its returning to its normal position as shown in Figs. 5 and 6.

With the spring 26 loaded to bring it into the before-mentioned straightened position, the opposite end of the filament 22 is welded or otherwise secured to the spring intermediate the ends of the latter as at 29. Upon release of the physical or mechanical force acting on the spring, it is readily seen that the filament is lightlyspring loaded and holds said spring in the described straightened position against its natural biasing action. Furthermore, it is seen that the elements !5, 2|, 22, 26, 2d and I1 are electrically connected in series forming the filament circuit of the tube In.

Terminal lead 13 mounts a Wire 38 having a right angle bend forming a pair of legs. The function of this wire will later be described. The end of the shorter leg of wire 39 is welded in an intermediate position on lead 18 and another loop of wire, generally indicated as 3!, is welded near the extreme upper end of the lead I8. This loop '31 comprises a getter assembly.

Referring now to Fig. 8, there is shown therein a bridge circuit comprising three resistors 33, 34 and 35 and the tungsten filament diode l9. Thisv diode with its network (in the present instance comprising the resistances 33, 3d and 3.5)

is the primary control unit of the voltage regulator. The input of the bridge circuit is derived from the secondary 36 of a transformer 31, the primary 38 of which is connected across the A. C. input line 39 and 49, the primary being in series with a winding of an autotransformer as will presently appear.

The transformer secondary 36 is connected to a rectifier tube 4! and the D. C. output of this tube is in turn connected to the input terminals 22 and d3 of the bridge 33, 3d, and It, previously described. Connected across the other junction points of the bridge circuit is the input circuit of an amplifier tube 46. Tube is supplied with filament current by means of a secondary winding 41 of a power transformer 38, the primary d8 of which is connected directly across the line 3940. Plate current is supplied to tube 66 from a secondary 5!) of the power transformer 48 through a full wave rectifier 5i and thence over conductors 52, 53, 54, 55, the saturating winding 56 of a saturable core reactor 51 and a conductor 58 to the plate of the tube 45.

Saturable cor-e reactor 51 is provided with an alternating current winding 59 which winding is in series with a portion 60 of the winding of an autotransiormer 6!, the other portion 62 of the winding of said autotransformer 6| being in series with the primary 3% of the transformer 31 as-previcusly mentioned. Transformer 3'! is also provided with a secondary 63 which secondary is connected by means of conductors B4 and 65 to the input of a bridge type rectifier composed of four selenium rectifiers 5B, 51, 63 and 59. The output of the rectifier is in turn connected by means of conductors m and H to the output terminals 12 and'l3. It will be noted that conductor '10 does not lead directly to terminal '12 but instead passes through a portion of a choke coil 14 which serves to filter out any ripple which might be present in the output. A condenser 15 is connected across the output terminals to accentuate the filtering action.

The filament of tube It is in electrical connection through spring 25, element 24 and H, and conductor 16 to positive polarity of the D. C. output and the other end of the filament connection through spring 26, elements 24 and I1, tor 11, a variable resistance 18, conductors 19 and 80, a variable resistance 8!, and a conductor 82 to terminal 13. In other words, the filament of the diode N3 is connected across the D. C. output and the temperature of said filament is varied in accordance with variations in said output.

The conductor or lead 16 instead of being connected to the conductor H3 at the place shown may be connected to said conductor at a point between the connections of condenser 15 and a condenser 83 with said conductor. This connection is sometimes advantageous since it utilizes the resistance of a coil 74 to vary the character of the load compensation.

From the above it will be seen that the basic power circuit comprises the autotransformer 6i and the saturable core reactor 5'7, this reactor being in series with the primary of the autotransformer. The portion 62 of the autotransformer 6! is connected in series with the primary winding 33 of transformer 31. Consequently, variation of the impedance of the saturable core reactor 51 will vary the voltage impressed on the primary 50 of the autotransformer GI and will thereby vary the voltage supplied to the rectifier transformer 31.

Thus, a decrease in reactor impedance will increase the portion of the input voltage which is impressed on the autotransformer primary 60 and will result in an increase in output voltage across output terminals 72 and 13. Conversely, an increase in the impedance of reactor 5'! will result in a decrease in the output voltage across terminals I2, 13.

To provide means for varying the reactor impedance by the proper amount to restore the output voltage to its original values at such times as it may vary due to changes in load or input voltage, the electronic control circuit heretofore described is provided. Thus, any change in output voltage across terminals l2, 13 will result in a change in temperature of the filament of diode iii which results in a change in the cathode emission of this tube and a relatively great change in the plate resistance of the tube. The signal voltage taken oil across the junction point as and filament cathode 22. is applied to the beam power tube 56, the output of which is in turn fed over a circuit heretofore described to the primary winding 50 or the saturable reactor 51.

In order to make the operation clear it will be assumed that a rise in output voltage has occurred due to a reduction of the load or a rise in input voltage or both. This increased output voltage across terminals ?2, [3 results in the application of a greater voltage to the diode filament and additional. heating of that filament. With increased heating the cathode of the diode I produces increased emission and thus reduces the plate resistance of the tube. Since diode it forms an arm of a bridge circuit, as previously decribed, a change in its plate resistance will change the balance condition of the bridge resulting, in the present instance, in the application of a more positive potential to the control grid of the beam power tube 45.

This positive grid signal results in a sharp increase in the plate current of the tube 40 and consequently produces an increased saturation of the saturable core reactor 5?. This increased D. C. saturation of the reactor 51 results in an increase in A. C. impedance and in turn results in lowering of the voltage in the rimary 38 of transformer This in turn results in a reduced voltage applied across the rectifier unit and consequently reduced output voltage across terminals i2, 13. Should the filament of diode i0 break or burn out, a similar action of the circuit just described results when the spring wire 2t is biased into electrical contact with wire 30 shunting a positive voltage to the grid of tube 46 but the circuit will not return to normal operating condition until the burned out tube is replaced.

With the exception of the filament of tube it becoming broken or burned out the action described immediately above will continue until an equilibrium point is attained, i. e., until the net change in output voltage is suficient to compensate for the changed conditions in the control circuit. The gain of the control system is of such magnitude that the direct current output voltage will be maintained constant within a tolerance of plus or minus 0.5%.

Tube 41 has already been described as a rectifier in the D. C. power supply for the bridge circuit diode Hi. This rectifier tube 41 is supplied with filament heating current by means of a secondary as of the transformer 48. Tube 5| has been described as supplying plate currents to the tube It and, of course, supplying current to the saturable core reactor Winding 56. This tube 5i is supplied with filament heating current by means of a secondary winding of the transformer 48.

A variable resistance Si is supplied in the circuit to the diode filament, adjustment of this resistance serving to adjust the output voltage to any desired point within the range of operation of the regulator. In order to compensate for variations in the input voltage a potentiometer i3 is supplied, this potentiometer serving to adjust the bias on tube 40 and thereby compensate for variations in the voltage input.

A variable resistance 58a is supplied in the output of the rectifier in order to permit compensation for load variation. It will be clear that as the load increases the drop through resistor 08a will likewise increase and thus the current flowing in the filament circuit of the diode it will be proportionally varied and the resistance of the cathode anode circuit of the diode will then compensate for the load change.

As will be obvious the variation of the resistance in the filament circuit of the diode I0 varies the value of the output voltage necessary to obtain a given diode filament temperature and will thus control the output voltage. A resistor 8%: is connected between the plate and screen of the beam power tube 4 3, this resistor serving as a swamping resistor to absorb conductive surges which originate in the winding 56 of the saturable core reactor 5i. This is necessary because of the very high inductance of this Winding.

Inserted in the line or conductor 54 is a resistance 88 while a resistance 81 is inserted between such line or conductor and the line or conductor 5d and the lines or conductors l0 and 80. Located in the line from the Winding 30 of transformer 31 is a resistance 09, the same being in series with a condenser t i. Another condenser 90 is located in the lead of the plate of tube ii while a condenser 02 is connected across the tube 5| and yet another condenser 93 is connected across the outputs it and I.

The particular voltage regulator which is shown in Fig. 8 was designed to provide an output voltage of 12 volts D. C. when operated from a supply of volts single phase A. C. and to saturate the saturable coil reactor 5'. when the filament of diode i0 is broken or burned out as before described to suppress the high over voltage of the output that would follow. The unit was operable on a supply voltage having a maximum variation of 15% and operating at a frequency of from 50 to 60 cycles per second. The output voltage was adjustable from 11 to 13 volts, the output load being from 5 to 8.5 amperes. It was found that the output voltage could be held to within plus or minus 1% of the preset desired Resistance '18 Potentiometer 8! Resistance 89 Condenser 89 15 ohms variable 20 ohms 47,000 ohms it microfarad Condenser 9i 1% microfarad Condenser 92 4 microfarad Condenser 93 8,000 microfarads Condenser i5 8,000 microfarads Condenser 83 25 microfarads In the specific unit above mentioned, the vacuum tube It is of the type known as the 2AS15, a temperature limited diode having a spring loaded tungsten filament made by Sorensen & Company, Inc. of Stamford, Connecticut. The remaining three tubes are standard tubes, tube A i, being a 2X2 tube, tube 5! a 5Y3 tube, and tube 45 being a 6L6 beam power tube. These three tube types are manufactured by the Radio Corporation of America and others under these designations.

The tube It with filament intact as used in an. operable circuit is best shown in Figs. 2, 3 and a and in diagram in Fig. 8. Said filament is connected in closed circuit across the output of conductors 78 and 13 as shown in Fig. 8 thereby effecting the electronic emission of the filament to plate due to voltage fluctuations in the output leads. It will be noted that the conductor 72 of positive polarity is electrically connected to the filament 22. Another electrical connection 32 outside the tube connects the plate 20 to the terminal lead 18 thence to the right angle element 30. It is here noted that element til and the spring 26 are in spaced relation and therefore in open circuit with respect to each other as can be seen in Figs. 2, 3 and 7.

Should the filament break or burn out in a tube it not provided with a spring loaded filament, the grid of power tube 56 becomes highly negative thereby causing an over-voltage 30-40% above normal in the D. C. output. This condition is overcome when the spring loaded filament of tube it burns out. The biasing action of the spring 25 moves its upper end over to the left bringing it into electrical contact with the outer leg of the bent wire 39 thereby closing a circuit from conductor 75 through elements ll, 25, 26, 3B, 18 and lead 32 to the plate 2% and shunting to the grid of tube 45 a positive voltage for reducing the D. C. output voltage. This prevents damage to any instruments in the output circuit. More specifically, the failure of the filament in diode it results in such diode becoming a short circuit rather than an open circuit insofar as the bridge or balancing circuit is concerned.

Having thus set forth the nature of our invention, what we claim is:

1. A voltage regulator for regulating the source of electrical power and controlling the voltage across a load circuit comprising, a bridge circuit with output terminals and including three resistors and a vacuum tube diode, said diode having an anode and a filamentary cathode, said cathode connected to the load and being electron emissive in proportion to the temperature thereof, the output voltage of said bridge circuit depending upon the emissivity and corresponding impedance of said diode, said bridge circuit connected by regulating means to the source to control the voltage thereof, switching means within the tube held open by the filamentary cathode and closing when the filament fails, thereby connecting the anode with the cathode and changing the bridge output volt age to lower the voltage across the load.

2. A voltage regulator for regulating a source of electrical power and controlling the voltage across a load circuit comprising, a bridge circuit with output terminals including three re sistors and a vacuum tube diode, said diode having an anode and a filamentary cathode, circuit. means connecting the load with the cathode to apply a voltage thereto in proportion to the load voltage, an amplifier circuit connected to the bridge output terminals and responsive to the degree of unbalance thereof, the output of said bridge depending upon the emissivity and corresponding impedance of said diode, switching means within the tube held open by the filamentary cathode and closing when the filament fails, thereby connecting the anode with the cathode and changing the bridge output voltage to lower the voltage across the load.

3. A voltage regulator for regulating a source of alternating current power and controlling the voltage across a load circuit comprising, a bridge circuit with output terminals including three resistors and a vacuum tube diode, said diode having an anode and a filamentary cathode, rectifier means connected to the source of alternating current for supplying said bridge circuit with direct current, circuit means connecting the load with the cathode to apply a voltage thereto in proportion to the load voltage, an amplifier circuit connected to the bridge output terminals and responsive to the degree of unbalance thereof, the output of said bridge depending upon the emissivity and corresponding impedance of said diode, switching means within the tube held open by the filamentary cathode and closing when the filament fails, thereby connecting the anode with the cathode and changing the bridge output voltage to lower the voltage across the load.

4. A voltage regulator for regulating a source of alternating current power and controllin the voltage across a load circuit comprising, a bridge circuit with output terminals includin three resistors and a vacuum tube diode, said diode having an anode and a filamentary cathode, rectifier means connected to the source of alternating current for supplying said bridge with direct current, circuit means connecting the load with the cathode to apply a voltage thereto in proportion to the load voltage, an amplifier circuit connected between the bridge output terminals and a saturable core reactor which is connected to the source circuit, the output of said bridge depending upon the emissivity and corresponding impedance of said diode, switching means within the tube held open by the filamentary cathode and closing when the filament fails, thereby connectin the anode with the cathode and changing the bridge output voltage to alter the current in the saturable core reactor and lower the voltage across the load.

5. A voltage regulator for regulating a source of alternating current power and controlling the voltage across a load circuit comprising, a bridge circuit with output terminals and including three resistors and a vacuum tube diode, said diode having an anode and a filamentary cathode, rectifier means connected to the source of alternating current for supplying said bridge with direct current, circuit means connecting the load with the cathode of said diode to apply a voltage thereto in proportion to the load voltage for determining the balance condition of the bridge,

an amplifier circuit connected between the bridge output terminals and a saturating winding of a saturable core reactor, an alternating current winding on said saturable core reactor connected to the source circuit, the output of said bridge depending upon the emissivity and corresponding impedance of said diode, switching means within the vacuum tube diode which is held open by the filamentary cathode and which is closed when the filament breaks, thereby connecting 2,621,322 9 the anode with the cathode and changing the UNITED STATES PATENTS bridge output voltage to alter the current in the Number Name Date saturating winding of the saturable core reactor 1 528 054 Harris Mar. 3, 1925 and to l w r the Voltage a ross the loa Murray Mar- 24 LEO L. HELTERLINE, JR. 5

1,969,955 Thomas Aug. 14, 1934 MARCELLUS BEST, JR. ADOLPH BUNBLASKY 2,200,443 Dench May 14, 1940 2,401,096 Paradise May 28, 1946 2,414,242 Potter Jan. 14, 1947 REFERENCES CITED 2,455,143 Sorensen Nov. 30, 1948 The following references are of record in the 10 file of this patent: 

